Nu-(hydroxy aryl) pyrroles as deterioration retarders



Patented Nov. 22, 1949 UNITED STATES- N-(HYDROXY' A'IYL) rmmoms as DETERIORATIONiRETARDERS Frank R. Valentine, Jr., Naugatuck, Conn as.-

signor 'to United States Rubber Company, New 'York, N. Y., a corporation of New Jersey No Drawing. Application November 20,, 1945, 1 Serial No. 629,922

J: NphenyleneOH (Formula I) wherein N, H, and C represent nitrogen, hydrogen,

and carbon respectively; phenylene refers. to a divalent benzene ring; and R refers to hydrogen, alkyl, or aryl. Formula II is given to show the numbering used in the general Formula I of the compounds i N-Op (FormulaII) Exemplary of such compounds are the following:

N-(p-hydroxy phenyl) -2,5-dimethyl pyrrole N- (p-hydroxy phenyl) -2,5-diethyl pyrrole N- (p-hydroxy phenyl) -2,5-dibutyl pyrrole N-(o-hydroxy phenyl) -2,5-dimethyl pyrrole N- (m-hydroxy phenyl) -2,5-dimethyl pyrrole N- (p-hydroxy phenyl) -pyrrole N- (o-hydroxy phenyl) -pyrrole N-(p-hydroxy phenyl) -2,5-diphenyl pyrrole N-(o-hydroxy phenyl) -2,5-diphenyl pyrrole In general, these pyrroles may be prepared by refluxing a solution of the primary amino compound and a 1,4-dicarbonyl compound in a suitable solvent, such as ethanol, methanol, or water. No catalyst is necessary, but usually the addition of a trace of acid, such as acetic acid, hastens the reaction of the two components. Examples of the 1,4-dicarbony1 compounds which may be used are acetonyl acetone, 1,2-dibenzoylethane, and succinic dialdehyde.

'12 Claims. (01. 26045;93)

phenyl) -'2','5-dimethyl pyrrole may be prepared by dissolving- 109 grams (lmdlc) ofp-amino phenol in 400 cc. of alcohol,-adding I25 grams ofa'cetonyl acetone (1 mole), 15 drops of glacial acetic acid and-refluxing the solution 4-5 hours; The mixture is cooled, drops of 35% sodium hydroxide added, and the alcohol removed in vacuo. The residue on distillation in vacuum yields 164 grams (138%) of N-(p-hydroxy phenyl)-*Zfi-dimethyl pyrrole, boiling range 145-150 =6; at-1' mm., a yellow oil crystallizing on cooling and meltingat .99-l02 C.

These compoundswareuseful as preservatives for rubber, and may be applied especially for stabilizing an uncuredtrubberybutadiene-styrene copclymer (Gr-RS) againstthe ei'iects oi -heat, As an example, 1.5 parts of N'- (p-hydroxy phenyl)- -2,5-dimethyl pyrrole-are added-.xtalllO-partsof the unstabilizedbutadiene-styrene copolymer and samples placed.-

an oven :at.2l-2ft-Fi Thesamp'les are examined periodically andzthe test discontinned when the samples show any resinification or cracking. The time in hours to this point is given in the table.

1 Test stopped at the end of this time.

The N-(hydroxy aryl) pyrroles disclosed herein are uniquely superior, as antioxidation catalysts, to the corresponding N-(amino aryl) pyrroles. For example, in a similar test to the above, 1.5 parts of N-(p-amino phenyl)-2,5-dimethyl pyr- 49 role, gave protection, in duplicate tests for but 24 and 48 hours. Control stocks containing no antioxidant resinify in about 24 hours.

This invention may be applied to the preservation of, broadly, natural rubber compositions as well as artificially-prepared rubber compositions, such as polychloroprene, olefin polysulfides, butadiene polymers, modified butadiene polymers (Buna N and Buna S), and including reclaims, and latices of such compositions.

The antioxidant may be incorporated in any type of rubber composition, such as those used for automobile tires and tubes, hose, belting, sheet and thread rubber, rubberized fabrics, molded goods, boots and shoes, etc., whether vul- More specifically, in illustration, N-(p-hydroxy canized in a mold, in open steam, in hot air, or

in the cold by the so-called acid process. The proportion of the antioxidant may vary from about 0.1% to although either smaller or greater proportions may be found useful. If the material to which it is added is a liquid such as rubber cement or van oil, the antioxidant may be dissolved therein in a suitable small proportion. The antioxidant may be incorporated into solid substances by milling or mastication, and prepared for incorporation into dispersions or solutions either in powder, paste or solution form, or applied in such forms for incorporation by diffusion, to the surface of vulcanized or unvulcanized rubber goods. 7

Having thus described my invention, what I .claim and desire to protect by Letters Patent is:

5. A sulfur-vulcanizable rubber compositioncontaining from 0.1 to 5 percent of an N-(p-hydroxy phenyl) -2,5-dialkyl pyrrole, and in which the sulfur-vulcanizabie rubber is from the class consisting of natural rubber, and butadienestyrene copolymer synthetic rubber.

6. A sulfur-vulcanizable rubber composition containing from 1.0 to 5 percent of N-(p-hydroxy phenyl) -2,5-dimethy1 pyrrole, and in which the sulfur-vulcanizable rubber is from the class consisting of natural rubber, and butadiene-styrene copolymer synthetic rubber.

7. A rubbery butadiene-styrene copolymer composition containing from 0.1 to 5 percent of an N -(hydroxy phenyl) pyrrole.

8. A rubbery butadiene-styrene copolymer composition containing from 0.1 to 5 percent of an N-(p-hydroxy phenyl) -2,5-dialky1 pyrrole.

9. A rubbery butadiene-styrene copolymer composition containing from 0.1 to 5 percent of N-(p-hydroxy phenyl) -2,5-dimethy1 pyrrole.

10. A natural rubber composition containing from 0.1 to 5 percent of an N-(hydroxy phenyl) pyrrole.

11. A natural rubber composition containing from 0.1 to 5 percent of an N-(p-hydroxy phenyl) -2,5 -dia1kyl pyrrole.

12. A natural rubber composition containing from 0.1 to 5 percent of N-(p-hydroxy phenyl) 2,5-dimethy1 pyrrole.

FRANK R. VALENTINE, JR.

REFERENCES orrno The following references are of record in the OTHER REFERENCES Hazlewood et 91., Journal Proceedings Royal Society of New South Wales, pages 921-102, March 1937.

Certificate of Correction Patent No. 2,489,000 November 22, 1949 FRANK R. VALENTINE, JR.

It is hereby'certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: I

Columnl, line 30, for that portion of the formula reading 4CN=C read 4UH=C; column 4, line 1, for 1.0 read 0.1;

and that the said Letters Patent should be read With these correc same may conform to the record of the case in the Patent Ofifice. Signed and sealed this 7th day of March, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oommz'ssz'oner of Patents.

tions therein that the 

